#include <fstream>

using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int n;
long long st, dr, mid, sol, i;
bool zero(int x){
    int number_of_zeros = 0;
    for(i = 5; i <= x; i+=5){
        int a = i;
        while(a % 5 == 0){
            number_of_zeros++;
            a = a / 5;
        }
    }
    if(number_of_zeros >= n)
        return true;
    return false;
}
int main()
{   f >> n;
    st = 1; dr = 5 * n;
    while(st <= dr){
        mid = (st + dr) / 2;
        if(zero(mid) == 1){
            sol = mid;
            dr = mid - 1;
        }
        else
            st = mid + 1;
    }
    g << sol;
    return 0;
}